diff --git a/libavcodec/pgssubdec.c b/libavcodec/pgssubdec.c
index 0d307f5302..e567f53ab4 100644
--- a/libavcodec/pgssubdec.c
+++ b/libavcodec/pgssubdec.c
@@ -33,7 +33,7 @@
 #include "libavutil/imgutils.h"
 #include "libavutil/opt.h"
 
-#define RGBA(r,g,b,a) (((a) << 24) | ((r) << 16) | ((g) << 8) | (b))
+#define RGBA(r,g,b,a) (((unsigned)(a) << 24) | ((r) << 16) | ((g) << 8) | (b))
 #define MAX_EPOCH_PALETTES 8   // Max 8 allowed per PGS epoch
 #define MAX_EPOCH_OBJECTS  64  // Max 64 allowed per PGS epoch
 #define MAX_OBJECT_REFS    2   // Max objects per display set